Deforestation near Coffs Harbour
coincided with 0.6C temperature rise, which had ‘catastrophic’ effect of
attracting fish
Monday 14 November 2016
20.50 GMT Last modified on Tuesday 15 November 2016 01.46 GMT
Herbivorous tropical fish have
destroyed kelp forests in northern New South Wales, showing that even small
increases in ocean temperature can lead to kelp deforestation, an Australian
study has found.
The University of NSW study,
published in the Proceedings of the National Academy of Sciences on Tuesday,
found that the disappearance of kelp from waters near Coffs Harbour coincided
with a threefold increase in the number of tropical fish in the region.
The deforestation coincided with
an 0.6 degree temperature rise. While that was not enough to directly impact
the kelp, lead author Dr Adriana Vergés said it had the “truly catastrophic”
effect of attracting hungry fish.
The study examined video footage
of 12 sites between 2002 and 2011. In 2002, six of the sites contained kelp. By
2010, all the kelp was gone.
The proportion of kelp showing
signs of bite marks increased from less than 10% in 2002 to more than 70% in
2008, before there was no kelp to measure. At the same time the proportion of
tropical fish in the ecosystem increased from less than 10% to more than 30%.
Most prolific were surgeonfish,
which increased from 9% of the local fish population in 2002 to 33% at the end
of the study period in 2011.
Once the kelp had been removed,
the ecosystem changed “quite dramatically” to become more tropical, in a trend
Vergés said could potentially be seen globally.
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